Size

• Mercury is the closest planet to the Sun. It is an average of 36 million miles way from it, but due to its elliptical orbit, it can get as close as 28.5 million miles. The farthest Mercury gets from the Sun on its orbit is approximately 44 million miles. Just a little larger in size than our moon, Mercury is the smallest of the planets now that Pluto has been deemed not to be a planet.
  
  

Time Frame

• The Mercurian year is much shorter than a year on Earth, as its distance to the Sun means that it takes much less time to complete one full orbit. Mercury whizzes around the star in 88 Earth days, meaning that more than four years pass on Mercury to every one of ours. However, a day on Mercury lasts almost two Earth months. This is because it takes Mercury more than 58 Earth days to complete one rotation on its axis.
  
  

Significance

• Mercury is very hard to observe as it always seems to be near the brightness of the Sun from Earth. It is visible only at sunset or near sunrise and is so close to the horizon that its image is distorted by our atmosphere. The intense heat from the Sun makes life impossible on Mercury, at least life as we know it. The surface of Mercury is scorched during the day, over 800 degrees F, but the side that is not facing the Sun is very cold, sometimes reaching 270 degrees F below zero. There is no atmosphere to speak of. Only half of Mercury's surface has been detailed due to the difficulty of observing the planet. The planet was long thought to take the length of its year, 88 days, to rotate once on its axis, but that has now been proven false.
  
  

Considerations

• The Sun on Mercury would appear to be triple the size of what it appears from Earth because of how close Mercury is to it. Mercury is very much like our moon--it has a surface pocked with craters. Mercury appears to cross the face of the Sun on rare occasions, which to astronomers are known as transits.
  
  

History

• Mercury was one of the five known planets to the ancients. Its speed, due to its nearness to the Sun, gave it its name; it is named after the Roman god Mercury, who was the swift winged messenger to the gods. The renowned astronomer Copernicus, for all his discoveries, was never able to see Mercury even once because it was so close to the Sun.